ES2793019T3 - Measuring device and pressure measuring system comprising a pressure sensor - Google Patents

Abstract

Vehicle tire pressure measurement device (1; 101) including: - a sensor (3; 103) including a printed circuit board (4; 104) having a portion intended to be subjected to pressure to be measured, the printed circuit board comprising extenders (10, 11; 110, 111) mounted on said portion to measure a deformation of the printed circuit board under the influence of said pressure, the sensor being intended to be secured to the tire whose pressure to be determined, and - a fixed portion (5; 105) intended to be secured to the vehicle opposite a path of the sensor for receiving measurements acquired by the sensor, the printed circuit board including a first main face and a second main face, sensor components serving as coupling components between the sensor and the fixed portion of the sensor being arranged on the second main face of said printed circuit board outside the por tion intended to be subjected to the pressure to be measured.

Description

DESCRIPTION

Measuring device and pressure measuring system comprising a pressure sensor

The invention relates to a pressure sensor. The invention also relates to a measurement device, as well as to a pressure measurement system comprising said sensor.

Technological background of the invention

In the aeronautical field, pressure sensors associated with landing gear tires are generally attached to the rims of said tires and transmit their data to a computer on board the aircraft. These sensors generally turn out to be complex and thus generally include strain gauges and means of processing the measurements made by the strain gauges.

Document GB 2394055 describes a pressure sensor comprising a plate superimposed on a printed electrical circuit, the plate comprising portions of reduced thickness and the circuit comprising strain gauges arranged at the level of said portions.

Document WO 02/14089 describes an apparatus for measuring the pressure of a vehicle tire comprising a sensor partly arranged on the tire, a mobile antenna connected to the tire in communication with the sensor on the one hand and on the other hand with a fixed antenna, mounted on the vehicle, of the measuring device.

Document DE 69907375 describes a vehicle wheel tire comprising a printed circuit board comprising strain gauges that measure a deformation of an annular core of the tire, the printed circuit board being integrated into the tire.

Object of the invention

One purpose of the invention is to propose a pressure sensor with a simplified structure, as well as a measurement device and a pressure measurement system comprising said sensor.

Brief description of the invention

In order to achieve this purpose, a device for measuring the pressure of a vehicle tire is proposed according to claim 1. The measuring device includes a printed circuit board having a portion intended to be subjected to the pressure at measuring, the printed circuit board comprising deformation detectors mounted on said portion to measure a deformation of said portion under the influence of said pressure.

Thus, the printed circuit board serves directly as a deformable portion and the deformation detectors are therefore directly mounted on the printed circuit board, not requiring the additional specific support sensor.

Advantage is therefore taken of the intrinsic characteristics of a naturally elastically deformable printed circuit board to simplify the sensor structure.

Therefore, the sensor turns out to be relatively simple in structure.

On the other hand, due to its simpler structure, the sensor turns out to be less sensitive to its surroundings, in particular less sensitive to temperatures and vibrations, which is particularly useful when the sensor is placed in a demanding environment such as, for example , around or on an aircraft tire.

Furthermore, the pressure sensor is also less expensive.

In addition, the pressure sensor is simpler to easily reproduce on a large scale, facilitating its production. Well understood, at least the portion of the sensor's printed circuit board intended to be subjected to the pressure to be measured is elastically deformable at least in the predetermined pressure range that the pressure sensor is to measure.

Typically, the predetermined pressure range is from 0 to 21 bar when the pressure sensor is intended to be used for measuring the pressure of an aircraft tire. The printed circuit board is, for example, in this case made of composite material. The printed circuit board 4 is for example made of a glass-epoxy matrix.

The invention also relates to a pressure measuring device that includes:

- a sensor such as previously described that is intended to be attached to an element whose pressure is to be determined, and

- a fixed portion that is intended to be secured opposite a sensor path for the reception of measurements acquired by the sensor and their transmission to the processing means.

The invention also relates to a system for measuring the pressure of a vehicle tire, the system including a device for measuring tire pressure and means for processing the measurements acquired by the measuring device, the means for measuring processing to be mounted on the vehicle away from the tire, including the measuring device:

- a sensor such as previously described which is intended to be rotatably secured to the tire, and

- a fixed portion arranged opposite a sensor path for receiving measurements acquired by the sensor.

In this way, the measuring device is the only one arranged near the tire, the processing means being totally remote from the tire. This makes it possible to limit the electronics in the immediate vicinity of the tire subjected to a very harsh environment and to place most of the electronics, and in particular the more sensitive electronics, in a more favorable environment such as, for example, the interior of the vehicle subjected to stress. a more forgiving environment.

The system turns out to be less sensitive to its surroundings, in particular less sensitive to temperatures and vibrations, which is particularly useful when the sensor is placed in a demanding environment such as around or on an aircraft tire.

In addition, the sensor is always integrated in the immediate vicinity of the tire, which allows the tire pressure to be measured both when the vehicle is stationary and in motion.

Brief description of the drawings

The invention will be better understood in light of the following description of the non-limiting embodiments of the invention with reference to the attached figures, among which:

Figure 1 is a schematic sectional view of the pressure sensor according to a first particular embodiment of the invention, as well as of a fixed portion associated with the sensor for receiving measurements acquired by the sensor of the associated measurement system;

Figure 2 is a diagram illustrating the system for measuring the pressure of a vehicle tire comprising the sensor and the fixed portion illustrated in Figure 1.

Figure 3 is a schematic sectional view of the pressure sensor according to a second particular embodiment of the invention, as well as of a fixed portion associated with the sensor for receiving measurements acquired by the sensor of the associated measurement system.

Figure 4 is a diagram illustrating the system for measuring the pressure of a vehicle tire comprising a sensor and a fixed portion according to a third particular embodiment of the invention.

Detailed description of the invention

With reference to the different figures, the pressure measurement system according to the first particular embodiment of the invention includes a measurement device 1 and means 2 for processing the measurements acquired by the measurement device 1. The pressure measurement system is here associated with an aircraft to measure the pressure of one of the aircraft's tires.

In this way, the measuring device 1 is associated with said tire and is arranged in the immediate vicinity of said tire and the processing means 2 are mounted on the aircraft to be away from said tire. Preferably, the processing means 2 is arranged in the pressurized atmosphere of the aircraft. The processing means 2 are integrated, for example, in one of the computers on board the aircraft.

The measuring device 1 includes a pressure sensor 3 arranged to be integral in rotation with the tire. The pressure sensor 3 includes here a printed circuit board 4 having an elastically deformable portion intended to be subjected to the pressure of said tire to be measured (symbolized by the arrows in figure 1). More precisely here, the printed circuit board 4 is secured to the rim of the tire to be rigidly fixed to the rim and, therefore, to the tire. Furthermore, the printed circuit board 4 is arranged so that its elastically deformable portion is directly in contact with the gas present inside the tire.

The measuring device 3 also includes a fixed portion 5 that is secured to the aircraft in the immediate vicinity of the tire. The fixed portion 5 is arranged, for example, on the axis of the landing gear that carries the tire, the pressure of which must be measured by the sensor 3. The fixed portion 5, of course, is secured to the vehicle to be opposite the trajectory rotary sensor 3 for receiving the measurements acquired by sensor 3 and transmitting them to the processing means 2, and for feeding the sensor.

Now the sensor 3, the fixed portion 5 and the processing means 2 will be successively detailed.

With respect to the sensor 3, the printed circuit board 4 is made of electrically insulating material. The printed circuit board 4 is, for example, made of composite material. The printed circuit board 4 is, for example, made of an epoxy glass matrix. The printed circuit board 4 includes a first main face 6 and a second main face 7 that extends opposite to the first main face 6 and parallel to said first main face 6. The two main faces 6, 7 are joined to each other by a or more side faces of the printed circuit board 4 according to the main shape of said printed circuit board 4 (for example, circular or rectangular). The two main faces 6, 7 are flat. The sensor 3 is arranged here so that the first main face 6 of the printed circuit board 4 is directly in contact with the gas present inside the tire, whereby the second main face 7 is, on the contrary, subjected at ambient pressure. around the tire

The printed circuit board 4 also includes a central hole 8 that extends from the second main face 7 in the direction of the first main face 6 without, however, opening at the level of said first main face 6. Therefore, the plate 4 of the printed circuit here has a general cuvette shape.

The printed circuit board 4 thus includes an area 9 of minimum central thickness delimited on the top by the bottom of the hole 8 and on the bottom by the first main face 6. It is this area 9 that here forms the elastically deformable portion of the sensor 3 intended to be subjected to the pressure to be measured. Although another part of the sensor 3 is subjected to the pressure of the tire, the sensor 3 is shaped so that only said zone 9 is deformed under the action of the pressure of the tire. For this purpose, the remainder of the sensor 3 has a thickness that is large enough not to be sensitive to the action of tire pressure.

For example, the printed circuit board 4 is shaped such that said board has a thickness of 2 to 3 millimeters at the level of the minimum thickness zone 9 and a thickness of approximately 5 millimeters at the level of the rest of said circuit board 4. printed. The printed circuit board 4 is further shaped so that the zone 9 has an area of between 1 and 2 square centimeters.

The printed circuit board 4 comprises deformation detectors on or in said zone 9 to measure a deformation of the printed circuit board 4 under the influence of the tire pressure. The strain detectors here are two in number and are arranged to form a measuring half bridge 12. Typically, the first detector 10 includes a first track 13 made of electrically conductive material and the second detector 11 includes a second track 14 made of electrically conductive material, the first track 13 and the second track 14 being arranged at the level of zone 9 ( inside said zone 9 and / or on the surface of said zone 9) and, therefore, are subject to deformation of said zone 9.

In this way, the deformation of zone 9 causes the deformation of said tracks 13, 14 and, therefore, a modification of their electrical properties representative of the deformation of zone 9 and, therefore, of the prevailing pressure on the tire. In fact, the variation in the length of each track 13, 14 due to its deformation causes a variation in its electrical resistance.

Tracks 13, 14 preferably include a serpentine portion that is more sensitive to deformations. The tracks 13, 14 are made, for example, of copper. The two deformation detectors 10, 11 are preferably identical for the symmetry of the half bridge 12.

Preferably, to improve the sensitivity of the deformation detectors 10, 11, the first detector 10 includes a first resistor 15 associated with the first track 13 and the second detector 11 includes a second resistor 16 associated with the second track 14. Said resistors 15 , 16 are also located on the printed circuit board 4 at the level of zone 9. Said resistors 15, 16 are connected in series with the track of the associated detector. Said resistors 15, 16 are, for example, nano-resistors.

The printed circuit board 4 also includes two capacitors associated with the half bridge 12 to resonate the half bridge 12 when the half bridge 12 is powered by the fixed portion 5 as will be seen later, a first capacitor 17 being associated with the first detector 10 (thus forming a first first detector / first capacitor assembly) and a second capacitor 18 being associated with the second detector 11 (thus forming a second second detector / second capacitor assembly).

This makes it possible in particular to improve the sensitivity of the half bridge 12.

The capacitors 17, 18 are connected in series with the associated detector at the level of the end of the track opposite to that connected to the associated detector resistor. Therefore, for each detector, the track is surrounded by the capacitor on the one hand and by the resistance on the other hand. The capacitors 17, 18 are arranged on the printed circuit board 4 outside of the zone 9. In this way, they are not subjected to the deformation of the zone 9. The capacitors 17, 18 include two surfaces of electrically conductive material (also called electrodes) separated by a portion of electrically insulating material. Preferably, at least one of the surfaces is arranged inside the printed circuit board 4 so that said board directly forms the electrically insulating material portion of the capacitor. The surfaces are made, for example, of copper. The surfaces are, for example, tracks built into the printed circuit board 4.

Furthermore, the measuring device 1 comprises means for supplying the two detector / capacitor assemblies through the fixed portion 5.

Preferably, the measuring device 1 is shaped such that the sensor 3 and the fixed portion 5 are in a high frequency alternating current electrical relationship. In this way, the supply means are here configured to supply the two detector / capacitor assemblies with high frequency alternating current. By high frequency, here is meant a frequency of at least 50 MHz. For example, the power means is configured to power the two detector / capacitor assemblies at a frequency between 50 and 300, and typically between 50 and 150 MHz. Preferably, the supply means is configured here to supply a high-frequency supply with an excitation frequency of approximately 100 MHz to the two detector / capacitor assemblies: the excitation frequency of the two assemblies, and therefore of the half bridge 12 measurement is therefore approximately 100 MHz.

For this purpose, the power supply means include a first transformer 21, whose primary is connected to the fixed portion 5 and whose secondary is connected to the sensor 3. More precisely here, the secondary is connected at one of its terminals to the first capacitor 17 by on the one hand, and to the second capacitor 18, on the other hand, and is connected at the other of its terminals to the first resistor 15 on the one hand and to the second resistor 16 on the other hand. The two detector / capacitor assemblies are thus powered in parallel.

Advantageously, the supply of the two detector / capacitor assemblies is therefore wireless, in particular thanks to the provision of a high-frequency alternating current supply.

The primary and secondary of the first transformer 21 preferably each include an inductance formed by a track of electrically conductive material directly integrated respectively in the fixed portion 5 and in the surface of the second main face 7 of the sensor 3. In this way, the first transformer 21 is not subjected to deformation of zone 9.

Said tracks are made, for example, of copper.

The first transformer 21 is configured so that the primary and secondary are resonated to increase the coupling between the primary and secondary of the first transformer 21.

Thus, the coupling losses between the fixed portion 5 and the sensor 3 are minimized.

Furthermore, by the two capacitors 17, 18, the two detector / capacitor assemblies are thus supplied not only with high frequency alternating current but also with resonance.

The measuring device 1 further includes first communication means between the sensor 3 and the fixed portion 5 for the reception by the fixed portion 5 of the measurements acquired by the deformation detectors 10, 11.

Typically, the first communication means includes a first LC circuit 31 (electrical circuit comprising in series a coil and a capacitor) associated with the first set and with the fixed portion 5, the coil of the first LC circuit 31 being connected to the first set. between the first track 13 and the first capacitor 17, and a second LC circuit 32 associated with the second set and with the fixed portion 5, the coil of the second LC circuit 32 being connected to the second set between the second track 14 and the second capacitor 18.

Each coil is, for example, an inductance formed by a track made of electrically conductive material. Here, the track is formed here directly on the surface of the second main face 7 of the sensor 3. The track is made, for example, of copper.

Each capacitor includes two surfaces of electrically conductive material separated by a portion of electrically insulating material. Preferably, for each condenser, one of the surfaces is arranged in the vertical of the second main face 7 of the sensor 3 and the other of the surfaces is arranged opposite to the fixed portion 5, the air separating the sensor 3 and the fixed portion 5 thus directly forming the electrically insulating material portion of the capacitor. The surfaces are made, for example, of copper. The surfaces are, for example, tracks directly integrated into the printed circuit board 4.

Therefore, the two LC circuits 31, 32 are connected to the fixed portion 5 by means of the capacitors of said circuits.

In this way, the electrical signals generated by the two detector / capacitor assemblies are transmitted through the capacitors of the two LC circuits 31,32 to the fixed portion 5. Advantageously, this transmission is therefore wireless.

Furthermore, due to their positioning, the first communication media are not subject to deformation of zone 9.

Therefore, the first communication means make it possible to recover, at the level of the measuring device 1, an indication of the imbalance of the two sets of detector / condenser representative of the deformation of the zone 9 under the action of tire pressure.

According to a particular embodiment, each resistance 15, 16 of the deformation detectors 10, 11 is equal (in the closest transformation ratio) to the characteristic impedance of the LC circuit associated with said detector.

This makes it possible to avoid standing wave circulation in said LC circuits 31,32.

According to a preferred embodiment, the measuring device 1 includes second communication means between the sensor 3 and the fixed portion 5 for reception by the fixed portion 5 of the power measurements at the terminals of the two detector / capacitor assemblies , measurements that can be directly related to the temperature of the two detector / condenser assemblies and, therefore, of the half bridge 12, based on the temperature coefficients of the different elements of the two detector / capacitor assemblies and the Thévenin generator equivalent to the supply means of said sets.

Therefore, these measurements can be used to weight the strain measurements made by the half bridge 12 as a function of the temperature of said half bridge 12.

The second communication means here include a third LC circuit 33 and a fourth LC circuit 34, both associated with the secondary of the first transformer 21 and with the fixed portion 5, the coil of the third LC circuit 33 being connected to one of the terminals of the secondary of the first transformer 21 and the coil of the fourth LC circuit 34 being connected to the other of the terminals of the secondary of the first transformer 21.

Each coil is, for example, an inductance formed by a track of electrically conductive material. Here, the track is formed directly on the surface of the second main face 7 of the sensor 3. The track is made, for example, of copper.

Each capacitor includes two surfaces of electrically conductive material separated by a portion of electrically insulating material. Preferably, for each condenser, one of the surfaces is arranged in the vertical of the second main face 7 of the sensor 3 and the other of the surfaces is arranged opposite the fixed portion 5, thus directly forming the air separating the sensor 3 and the fixed portion 5, the electrically insulating material portion of the capacitor. The surfaces are made, for example, of copper. The surfaces are, for example, tracks directly integrated into the printed circuit board 4.

Therefore, the third LC circuit 33 and the fourth LC circuit 34 are connected to the fixed portion 5 by means of the capacitors of said circuits 33, 34.

In this way, the electrical signals representative of the power supply of the two detector / capacitor assemblies are transmitted through the capacitors of said circuits 33, 34 to the fixed portion. Advantageously, this transmission is therefore done wirelessly.

Furthermore, due to their positioning, the second communication means are not subject to deformation of the zone 9. Therefore, the second communication means make it possible to recover, at the level of the measuring device 1, an indication of the power supply of the two detector / condenser assemblies, representative of the temperature of these two detector / condenser assemblies and therefore of the half bridge 12.

Therefore, it is observed that the sensor 3, which is the part of the pressure measurement system subjected to the most severe environment, includes a relatively limited number of components. This enables the quality of the pressure measurement to be improved.

Furthermore, the sensor 3 is particularly simple in terms of structure, since most of the components are directly integrated in the printed circuit board 4, for example, being formed by electrically conductive tracks arranged in or on the circuit board 4 printed. Actually, apart from the resistors, the various elements of the sensor 3 are created by routing to be incorporated directly into the printed circuit board 4 and formed by conductive tracks on said board 4. On the other hand, the resistors are placed on the board 4 of printed circuit, for example, by screen printing or by adding metallic foils (generally other than copper).

Furthermore, the deformation of the zone 9 has little or no impact on the various coupling components (power and communication) between the fixed portion 5 and the sensor 3, said components being arranged outside the zone 9.

Furthermore, there is no cable connection between the sensor 3 and the fixed portion 5: the coupling between the fixed portion 5 and the sensor 3 is done only by capacitive link (here for communication of measurements) or by inductive link (here for feeding). The coupling between the sensor 3 and the fixed portion 5 is therefore mixed (capacitive and inductive). On the other hand, the coupling between the sensor 3 and the fixed portion 5 is also of the high frequency alternating resonant type (at the level of the power supply, such as the communication of the measurements).

Advantageously, the coupling losses also turn out to be relatively low or almost zero, in particular due to the existence of the pairs of resonant circuits in series LC (first pair formed by the first circuit LC 31 and the second LC circuit 32 and the second pair formed by the third LC circuit 33 and the fourth LC circuit 34), due to the fact that the different couplings are of the high frequency alternating resonant type.

The sensor 3 thus described here has a measurement precision of between 0.1 and 0.3 bar, typically 0.2 bar.

On the other hand, it is observed that the series resonance of the two detector / capacitor assemblies makes it possible to limit or even suppress the reactive currents that tend to disturb the measurements. Indeed, the inductive appearance of the device will vary little due to the fact that it remains in, or close to, a resonance mode, which makes it possible to limit the reactive currents.

Actually, the supply current of sensor 3 always sees a real load while the supply voltage is differential and increases due to the modification of the complex impedances in sensor 3 (due to the fact that the detectors deform, a priori symmetrically, which implies a rotation of the vectors of the complex impedances in opposite directions).

This allows to improve the sensitivity of sensor 3.

As regards the fixed portion 5, here it includes a frame 40 rigidly fixed to the shaft and a coupler 41 which is in turn rigidly fixed to said frame.

The frame 40 includes cable connection means of the coupler 41 to the processing means 2. The cable connection means includes, for example, a connector 42 and a corresponding cable 43 connected at one end to said connector 42 and at the other end to a corresponding connector of the processing means 2. The cable 43 is preferably shaped to ensure a differential transmission of the different signals between the measuring device 1 and the processing means 2. Cable 43 is, for example, of the Quadrax type.

The coupler 41 includes a first main face 44 and a second main face 45 extending opposite to the first main face 44 and parallel to said first main face 44. The two main faces 44, 45 are joined together by one or more faces sides of the coupler 41 according to the main shape of the coupler 41 (eg, circular or rectangular). The two main faces 44, 45 are flat. The coupler 41 is arranged here so that the first main face 44 is opposite the second main face 7 of the sensor 3 when the sensor 3 is at the level of the coupler 41 in the course of its rotational movement. The coupler 41 is shaped here so that the first main face 44 of the coupler 41 has the same dimension as the second main face 7 of the sensor 3, however, the first main face 44 of the coupler 41 does not include a hole leading to its level. Therefore, the coupler 41 is not cup-shaped.

Preferably, coupler 41 is a printed circuit board. Therefore, as described above for the sensor 3, the different elements, in particular of the type of transformers, capacitors and coils that the coupler 41 can include, are preferably integrated directly into the printed circuit board, being formed, for example, by tracks of electrically conductive material arranged in or on the printed circuit board.

To ensure the transmission of the signals from the sensor 3 to the connection means of the frame 40, the first communication means include a second transformer 22 arranged on the coupler 41 and connected, on the one hand, to the connection means and, on the other hand part, to the capacitors of the first LC circuit 31 and of the second LC circuit 32. More precisely here, one terminal of the secondary of the second transformer 22 is connected to the first LC circuit 31 and the other terminal of the secondary of the second transformer 22 is connected to the second LC circuit 32. Therefore, the two detector / capacitor assemblies are connected in series to the fixed portion 5. Furthermore, each terminal of the primary of the second transformer 22 is independently connected to the connection means.

There is thus differential transmission of the signals generated by the two sets of detector / condenser, and representative of the pressure, to the processing means 2.

Furthermore, to guarantee the transmission of the signals representative of the supply of the two detector / capacitor assemblies to the connection means of the frame 40, the second communication means include a third transformer 23 arranged on the coupler 41 and connected on the one hand to the connection means and, on the other hand, to the capacitors of the third LC circuit 33 and of the fourth LC circuit 34. More precisely here, one terminal of the secondary of the third transformer 23 is connected to the third LC circuit 33 and the other terminal of the The secondary of the third transformer 23 is connected to the fourth LC circuit 34. Furthermore, each terminal of the primary of the third transformer 23 is independently connected to the connection means.

Therefore, there is differential transmission of the signals generated by the secondary of the first transformer 21, and representative of the supply of the two detector / capacitor assemblies, to the processing means.

Therefore, there is independence of the four lines connected, on the one hand, either to one of the primary terminals of the second transformer 22 or to one of the primary terminals of the third transformer 23 between them and, on the other hand, to the processing means via cable 43 with differential transmission.

On the other hand, to ensure the supply of the sensor 3, the primary of the first transformer 21, which is arranged in the fixed portion 5 is connected to the second transformer 22 and to the third transformer 23. One terminal of the primary of the first transformer 21 is here connected to the primary of the second transformer 22 and the other terminal of the primary of the first transformer 21 is connected to the primary of the third transformer 23.

On the other hand, the fixed portion 5 includes means for grounding the processing means. For this purpose, the grounding connection means includes a line 46 connected, on the one hand, to the primary of the first transformer 21 and, on the other hand, to the ground of the processing means 2 through the cable 43.

Preferably, as for the first transformer 21, the different transformers 22, 23 of the fixed portion 5 are tuned to the target driving frequency of 100 MHz. This optimizes coupling and reduces or even suppresses reactive currents.

Therefore, it is observed that the fixed portion 5, which is also part of the pressure measurement system subjected to a very severe environment, includes a relatively limited number of components. This enables the quality of the pressure measurement to be improved.

Furthermore, the fixed portion 5 turns out to be particularly simple in terms of structure since most of the components are directly integrated in the printed circuit board of the coupler 41, for example, by being formed by electrically conductive tracks arranged in or on the board. printed circuit

With respect to the processing means 2, they include a supply circuit 50 for supplying the supply means of the measuring device 1. For this purpose, the power circuit 50 includes a high-frequency alternating current power supply 51, which here therefore has an excitation frequency equal to approximately 100 MHz. The power circuit 50 further includes a fourth transformer 24 connected to said power supply 51.

Preferably, the processing means includes a power circuit 50 measurement circuit 52 for monitoring and possible control of the high frequency alternating current power source 51. Typically, the measurement circuit 52 is connected to the power circuit 50 by the synchronous detection means such as a synchronous demodulator 53.

The processing means 2 further includes a tire pressure measurement circuit 54. For this purpose, said circuit 54 includes a fifth transformer 25 for which its first terminal of the secondary is connected, through cable 43, to the first terminal of the primary of the second transformer 22 of the measuring device 1 and for which its second terminal of the secondary is connected, through the cable 43, to the second terminal of the primary of the second transformer 22. This ensures the transfer of the signals generated by the two detector / capacitor assemblies to the pressure measurement circuit 54 which will thus process these signs.

The fifth transformer 25 is also powered by the power supply circuit 50 of the processing means 2, here by connecting the secondary of the fifth transformer 25 to the secondary of the fourth transformer 24. The power supply of the two detector / capacitor assemblies is thus ensured. through the pressure measuring circuit 54, the cable 43 and the measuring device 1.

Therefore, the same cable links between the processing means 2 and the measuring device 1 ensure both the power supply and the transmission of the signals generated by the two detector / capacitor assemblies.

Furthermore, the processing means 2 includes a temperature measurement circuit 55 of the two detector / condenser assemblies and, therefore, of the half bridge 12.

For this purpose, said circuit 55 includes a sixth transformer 26 for which the first terminal of the secondary is connected, through the cable 43, to the first terminal of the primary of the third transformer 23 of the measuring device 1 and for which the second terminal of the secondary is connected, through the cable 43, to the second terminal of the primary of the third transformer 23. In this way, the transfer of the signals representative of the supply of the two detector / capacitor assemblies to the temperature measurement circuit 54 is ensured. process these signals well.

In fact, it is recalled that the supply voltage of the two detector / capacitor assemblies varies as a function of the temperature of said two assemblies due to the fact, in particular, of known intrinsic characteristics of the two assemblies. From the measurement of the supply voltage and the knowledge of these data, the temperature of these assemblies can thus be deduced from them.

On the other hand, sensor 3 is subjected to very large temperature variations compared to the rest of the system. Measuring the temperature (by studying the supply voltage) at the level of sensor 3 allows minimizing the influence of the variation of the electrical resistance of the supply line as a function of temperature and thus improving the precision of the measurement Of temperature. The temperature is thus advantageously measured at the level of the zone of the system most reactive in temperature.

In addition, to process the signals generated by the deformation detectors 10, 11 taking into account the temperature of the half bridge 12, the pressure measurement circuit 54 and the temperature measurement circuit 55 are connected to each other. The connection of the temperature measurement circuit 55 to the pressure measurement circuit 54 is made upstream of the fifth transformer 25, on the one hand, and upstream of the sixth transformer 26, on the other hand. In particular, this connection is made by means of synchronous detection means of the processing means 2. Typically, the pressure measurement circuit 54 includes a synchronous demodulator 57 arranged upstream of the fifth transformer 25 and the temperature measurement circuit 55 also includes a synchronous demodulator 58 arranged upstream of the sixth transformer 26, the two circuits being connected to each other. through said two synchronous demodulators 57, 58.

The temperature measurement circuit 55 thus allows its own demodulation (automatic synchronous) since the signals received in this circuit are never null, and it also allows controlling the demodulation of the pressure measurement circuit 54 whose signals can sometimes be null.

The demodulation of these two circuits is thus independent of the length of the supply line.

The sixth transformer 26 is also powered by the power supply circuit 51, here by connecting the secondary of the sixth transformer 26 to the secondary of the fourth transformer 24. The power supply of the two detector / capacitor assemblies is thus also ensured by means of the circuit 55 of temperature measurement, cable 43 and measuring device 1.

Therefore, the same cable links between the processing means 2 and the measuring device 1 ensure both the supply and the transmission of the signals representative of the supply of the two detector / capacitor assemblies.

According to a particular embodiment, the processing means 2 comprise a control circuit 59 for the output of the power circuit 50 (that is, the power line connected to the pressure measurement circuit 54 and the temperature measurement circuit 55 ).

This allows to evaluate the losses caused by the power line itself. In this way, these losses can be taken into account to estimate temperature and pressure measurements.

Furthermore, this enables the power circuit 50 to be controlled in order to control the power.

Furthermore, this makes it possible to identify a possible problem at the level of the supply circuit 50, such as a short circuit.

Unlike the rest of the pressure measurement system, the control circuit 59 is supplied with direct current. Typically, the control circuit 59 includes means for generating an electrical pulse 60 to the power line and means for detecting the return wave 61 after this pulse. The length of the supply line is thus measured by measuring the travel time and the amplitude of the return wave.

Advantageously, the quality of the supply line is thus monitored, the return wave passing through the shield of the fourth transformer 24 to return to the control circuit.

On the other hand, it is thus possible to estimate the electrical resistance of the power line from the measurement of the length of the power line and knowing the intrinsic characteristics of the power line.

The processing means 2 thus described thus make it possible to measure the tire pressure. In particular, the tire pressure can be measured continuously.

Preferably, as for the sensor 3 and the fixed portion 5, the different transformers of the processing means 2 are tuned to the target drive frequency of 100 MHz. This optimizes coupling and reduces or even suppresses reactive currents.

Preferably, the processing means 2 implement the following procedure for each new pressure measurement:

- audit of the power line by the control circuit 59,

- acquisition of representative signals of the supply of the half bridge 12 by the temperature measurement circuit 55,

- acquisition of signals representative of the deformation of the printed circuit board 4 by the pressure measurement circuit 54,

- estimation of the pressure from the audit, of the signals representative of the supply of the half bridge 12 and of the signals representative of the deformation of the printed circuit board 4.

With reference to FIG. 3, the pressure measurement system according to the second embodiment of the invention turns out to be identical to that of the first embodiment with the difference that the sensor 103 has a different shape.

Indeed, contrary to the first embodiment, in which the central hole extended from the second main face in the direction of the first main face without, however, opening at the level of said first main face, in the second embodiment, hole 108 extends completely into the interior of printed circuit board 104 without opening from said printed circuit board 104. The hole 108 is typically disposed in the center of said printed circuit board 104 (relative to the main faces 106, 107 of said printed circuit board 104). The hole 108 is arranged, for example, at one third of the height of the printed circuit board 104 (relative to the first main face 106 of said printed circuit board 104). The hole 108 has, for example, a height between 0.5 and 1 millimeter. Typically, hole 108 has a height of 0.5 millimeters when zone 109 is 2 millimeters thick, that is, 25% of the thickness of zone 109.

The zone 109 of central minimum thickness is thus always delimited superiorly by the bottom of the hole 108 and inferiorly by the first main face 106. However, since the hole 108 does not open this time, in particular in the second main face 107 of the printed circuit board 104, the hole 108 thus limits a deformation of the zone 109 by its ceiling (opposite to its bottom which delimits said zone 109). This advantageously makes it possible to avoid a significant deformation of the zone 109 in the event of overpressures, generally transitory, in the tire, a deformation that can damage or plastically deform said zone 109.

In particular, the printed circuit board 104 further includes an opening 119 extending from the second main face 107 in the direction of the hole 108 and leading into said hole 108. The opening 119 is preferably provided in the printed circuit board 104 so that it opens into the center of said hole 108. The opening 119 is, of course, of transverse dimensions (that is, according to the direction that goes from the first main face 106 to the second main face 107) smaller than those of the hole 108 so as not to approximate the shape of the cuvette of the first embodiment.

The opening 119 thus allows the passage of air to the hole 108, thus limiting too great a confinement of the zone 109.

Of course, the invention is not limited to the described embodiments and variant embodiments can be provided without departing from the scope of the invention as defined in the claims.

In particular, although here the sensor is associated with an aircraft tire, the sensor can be used to measure the pressure of any element other than an aircraft tire. In the same way, although here the system is associated with a tire of an aircraft, the system can be used to measure the pressure of a tire of any other vehicle, such as for example a tire of a motor vehicle.

Although here the various tracks and surfaces made of electrically conductive material are made of copper, these tracks and surfaces may be made of another material, for example Kovar (trade mark), ie FeNiCo alloy. The different elements described may be based on nanomaterials. For example, strain detectors may be made of nanomaterials. Although here most of the elements described are formed from tracks, said elements could be resistors, capacitors, coils, etc. placed on the associated support and not formed directly on the support.

Although here the capacitive coupling between the sensor and the fixed portion is made with the help of capacitors whose electrically conductive surfaces are flat, said capacitors may have a different shape. For example, the sensor and the fixed portion may be shaped such that one has a female portion, eg of revolution, coated with an electrically conductive surface and the other a male portion, eg, of revolution, coated with a surface. electrically conductive, the female portion extending into the male portion to form a capacitor. The female portion may be, for example, 20 microns high. The formation of the male portion can be done by mechanical machining or by laser machining.

Other interconnections between the different elements of the system than those described could be considered. For example, it is possible to subordinate the power supply of the power circuit based on the temperature measurement typically in order to have a maximum voltage at the terminals of the half bridge.

On the other hand, although here the coupling between the fixed portion and the sensor is made by capacitive connection for the communication of the measurements and by inductive connection for the power supply, the fixed portion and the sensor can be configured differently so that the Coupling between the fixed portion and the sensor is made by a capacitive connection for the power supply and by an inductive connection for the communication of the measurements.

In both cases, capacitive / inductive sharing allows connections to be more easily segregated.

The coupling between the fixed portion and the sensor can also be made by means of an inductive connection for the communication of the measurements as for the power supply, or it can also be made by a capacitive connection for the communication of the measurements as for the power supply. Figure 4 thus illustrates a coupling between the fixed portion and the sensor entirely by inductive connection. This embodiment illustrated in figure 4 makes it possible to have a measuring device with a simplified structure.

Of course, the sensor includes a printed circuit board that directly forms the deformable part of the sensor, the sensor may have a different shape. Therefore, the sensor can include deformation detectors, but no deformable portions. When the sensor will include a printed circuit board comprising a deformable part intended to be subjected to the pressure to be measured, the sensor may have a different shape than that described. For example, in the case of the second embodiment, the printed circuit board may not have an opening that connects the hole to the outside. This will make the sensor insensitive to variations in atmospheric pressure. In this case, the hole can be filled with air or also with a gas other than air, without the hole having contact with the environment outside said card. The orifice can thus be filled with an inert gas.

Of course, when the sensor will include a printed circuit board that comprises a part intended to be subjected to the pressure to be measured, at least said part will be elastically deformable at least in the predetermined pressure range that the pressure sensor will measure. Typically, the predetermined pressure range will be 0-21 bar when the pressure sensor is intended to be used to measure the pressure of an aircraft tire.

Claims (18)

1. Device (1; 101) for measuring the pressure of a vehicle tire including: - a sensor (3; 103) that includes a printed circuit board (4; 104) having a portion destined to be subjected to the pressure to be measured, the printed circuit board comprising extenders (10, 11; 110, 111) mounted on said portion to measure a deformation of the printed circuit board under the influence of said pressure, the sensor being intended to be secured to the tire whose pressure is to be determined, and - a fixed portion (5; 105) destined to be secured to the vehicle opposite a sensor path for receiving measurements acquired by the sensor, The printed circuit board including a first main face and a second main face, sensor components serving as coupling components between the sensor and the fixed portion of the sensor being arranged on the second main face of said printed circuit board outside of the portion intended to be subjected to the pressure to be measured. Device according to claim 1, in which the printed circuit board (4) includes a central hole (8) that extends from the second main face towards the first main face without, however, opening at the level of said first main face, the portion destined to be subjected to the pressure to be measured being thus formed by the zone (9) of minimum central thickness delimited superiorly by the bottom of the hole and inferiorly by the first main face. Device according to claim 1, in which the printed circuit board (104) includes a hole (108) that extends inside said printed circuit board without opening at the level of said first main face and said second main face, the portion destined to be subjected to the pressure to be measured being thus formed by the zone (109) of minimum central thickness delimited superiorly by the bottom of the hole and inferiorly by the first main face. Device according to claim 3, in which the printed circuit board (104) further includes an opening (119) extending from the second main face (107) in the direction of the hole (108) and leading into said hole . Device according to claim 3, in which the orifice (108) is filled with a gas other than air. Device according to one of the preceding claims, in which at least one of the deformation detectors (10, 11; 110, 111) includes a track of electrically conductive material arranged on or on the sensitive and printed circuit board (4) to the deformation of said plate. Device according to one of the preceding claims, in which the printed circuit board (4; 104) includes two deformation detectors (10, 11; 110, 111) forming a half bridge (12; 112) for measurement and two capacitors (17, 18; 117, 118) associated with the half bridge to resonate the half bridge when the half bridge is powered. Device according to one of the preceding claims, including means for supplying the sensor (3; 103) by means of the fixed portion (5; 105), the fixed portion and the sensor being configured to supply the sensor by power supply alternating high frequency. Device according to claim 8, in which the device is configured such that the high frequency is between 50 and 300 MHz. Device according to one of claims 8 to 9, in which the fixed portion (5; 105) and the sensor (3; 103) are coupled to each other without a cable connection. Device according to claim 11, in which the fixed portion (5; 105) and the sensor (3; 103) are coupled to each other by inductive and capacitive connection. Device according to one of the preceding claims, including means for measuring the temperature of at least the deformation detectors (10, 11; 110, 111). Device according to claim 12, in which the temperature measurement means include means for measuring the power supply of the deformation detectors (10, 11; 110, 111). Device according to one of the preceding claims, in which the fixed portion (10; 110) includes means for connection by cable to processing means remote from the device, said means of connection wired by cable comprising a cable (43; 143 ) capable of ensuring differential transmission of the different signals between the device and the processing means. Device according to one of the preceding claims, in which the fixed portion (5; 105) includes a printed circuit board that ensures the coupling of the fixed portion to the sensor (3; 103). 16. System for measuring the pressure of a vehicle tire, the system including a device for measuring the pressure of the tire according to one of the preceding claims and means for processing measurements acquired by the measuring device, the means being intended processing units to be mounted on the vehicle remote from the tire, the fixed portion being intended to be secured to the vehicle opposite a sensor path for receiving measurements acquired by the sensor and transmitting them to the processing means. System according to claim 16, in which the processing means (2) include a supply circuit (50) for the fixed portion and a control circuit (59) for an output of said supply circuit. System according to claim 17, in which the control circuit (59) includes means for generating an electrical impulse (60) to the supply circuit and means for detecting the return wave (61) after this impulse